The present invention relates to an apparatus and method for shipping and installing a linear actuator. More particularly, the present invention relates to shipping and installations straps for holding in a rectracted position the output member of a linear actuator, such as a hydraulic actuator, during transportation and storage and during installation of the actuator for operation of a mechanism.
Hydraulic actuator apparatus are known for operating a mechanism at a remote location by way of a master cylinder, for example, connected to a slave cylinder installed at the remote location. A conduit interconnects the master cylinder to the slave cylinder, and the hydraulic apparatus is filled with hydraulic fluid such that when the piston of the master cylinder is actuated, the piston of the slave cylinder, and consequently the piston rod or output member, are simultaneously actuated by displacement of the hydraulic fluid from the master cylinder to the slave cylinder through the conduit.
More particularly, it is known to provide such hydraulic apparatus for operating, for example, the release mechanism of a friction clutch. As disclosed in British patent specification No. 1,539,879, and in corresponding applications for United States Letters Patents, Ser. Nos. 911,477, now U.S. Pat. No. 4,407,125, now abandoned and 376,248 which are continuations of application Ser. No. 676,474, now abandoned, and in applications Ser. Nos. 338,165, now abandoned, and 400,276, now abandoned, all assigned to the same assignee as the present application, it is now known to pre-assemble friction clutch hydraulic release apparatus, by filling with hydraulic fluid the master cylinder, the slave cylinder, the conduit interconnecting the cylinders and a reservoir connected to the master cylinder, before shipment of the assembly to a motor vehicle manufacturer, for installation on a motor vehicle. Preferably, the hydraulic apparatus is filled with fluid maintained by a resilient diaphragm disposed in the reservoir of fluid, at a pressure slightly higher than atmospheric pressure to prevent introduction of atmospheric air into the system during transportation, storage and installation. Prior to installation, the piston rod, or output member, projecting from one end of the slave cylinder may become extended such that the over-all length of the slave cylinder, with the piston rod extended, may occupy more space than necessary in the shipping container, the rod may become bent or damaged while in transit or storage or become disconnected from the piston, the pressure of the fluid may drop below atmospheric pressures, thus causing air to be introduced into the hydraulic apparatus, and the slave cylinder piston rod must be manually retracted and held retracted during installation of the apparatus in the motor vehicle.
The principal object of the invention disclosed in prior application Serial No. 344,495 assigned to the same assignee as the present application is to provide a restraining strap for the output member of a linear actuator such as the piston rod of a slave cylinder of a pre-filled sub-assembly comprising a master cylinder, a slave cylinder and a conduit interconnecting the master cylinder with the slave cylinder. The object of the invention is achieved by providing a flexible, preferably plastic, strap having a portion maintaining the slave cylinder piston rod in a retracted position by attaching the end of the piston rod to the housing of the slave cylinder, the strap having appropriate weakened break-away sections defining one or more rupture portions, such that when the piston of the master cylinder is actuated for the first time, thus causing a thrust to be applied to the piston and piston rod of the slave cylinder, the strap is broken and the apparatus is enabled to operate in a normal manner.